Fix error on saving new multi-site

[olivier-nolbert]

https://www.seblod.com/community/forums/fields-plug-ins/seblod-4-multi-site-field-guest-only-group-doesn-t-have-a-default-value

If you need a quick fix on your website, you can run this SQL query : ALTER TABLE #__cck_core_sitesCHANGEguest_only_group guest_only_group INT(10) UNSIGNED NOT NULL DEFAULT '0';